The central instrument in a number of our protocols remains the biplane high-speed cineradiographic unit. It is being used to study the development of left ventricular hypertrophy in mongrel dogs. The cineradiograms are analyzed on a versatile plotter which allows us to rapidly digitize the graphic information and determine changes in left ventricular volume (LVV), left ventricular length (LVL), left ventricular wall thickness (LVT), left ventricular diameter (LVD), dp/dt, dl/dt, ejection fractions, wall stress, stroke work and blood flow. Three-dimensional diagrams of force-velocity-length can be constructed from the above variables to demonstrate changes in performance of the heart throughout the cardiac cycle. Mechanical interaction between left and right ventricular performance is also being investigated. With a new nonionic radiopaque material, Metrizamide, it is possible to visualize and study in situ all the cardiac valves. Other protocols involve the examination of the venous endothelium after exposure to water-soluble, radiopaque materials for the detection of leukocyte induced damage. Other studies on contrast materials are being conducted on the serum enzyme changes after cerebral angiography.